Power planes for a radio frequency (RF) metamaterial antenna

The present application is a non-provisional application of and claims the benefit of U.S. Provisional Patent Application No. 63/301,585, filed Jan. 21, 2022 and entitled “POWER PLANES FOR A RADIO FREQUENCY (RF) METAMATERIAL ANTENNA SEGMENT”, which is incorporated by reference in its entirety.

Embodiments of the present disclosure are related to wireless communication; more particularly, to power planes for radio frequency (RF) antenna elements of an antenna.

Metasurface antennas have recently emerged as a new technology for generating steered, directive beams from a lightweight, low-cost, and planar physical platform. Such metasurface antennas have been recently used in a number of applications, such as, for example, satellite communication.

Metasurface antennas may comprise metamaterial antenna elements that can selectively couple energy from a feed wave to produce beams that may be controlled for use in communication. These antennas are capable of achieving comparable performance to phased array antennas from an inexpensive and easy-to-manufacture hardware platform.

Some metasurface antennas using multiple bands and/or operating at high frequencies, such as Ka frequency, require many radio frequency (RF) metamaterial antenna elements for their operation. Moreover, some RF metamaterial-based antennas use more complex RF antenna element circuitry with multiple transistors, capacitors, timing signals and DC voltage sources. The area required to route control signals and DC voltages sources to the RF element driver circuits becomes too large for that kind of high-density designs. Furthermore, the minimum linewidth and gap between lines that can be used for such routing are limited by the process technology capability.

A radio-frequency (RF) antenna and method for using the same are disclosed. In some embodiments, an antenna includes an array of RF radiating antenna elements, a plurality of RF antenna element driving circuits coupled to the array of RF radiating antenna elements to supply tuning voltages to the RF radiating antenna elements, and one or more metal power planes, each of the one or more metal power planes coupled to supply a common voltage to two or more of the plurality of RF antenna driving circuits.

In the following description, numerous details are set forth to provide a more thorough explanation of embodiments of the present disclosure. It will be apparent, however, to one skilled in the art, that the teachings disclosed herein may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present disclosure.

Embodiments described herein include an antenna having a reduced number of routing lines. In some embodiments, the antenna is part of a satellite user terminal. In some embodiments, the antenna is a metamaterial antenna with radio-frequency (RF) radiating antenna elements such as, for example, described below. In some embodiments, the antenna includes drive circuitry for driving the antenna elements. In some embodiments, the drive circuitry uses transistor or other circuitry to drive voltage to the antenna elements. Embodiments disclosed herein includes method for decreasing the number of routing lines for the drive circuitry. For example, in some embodiments, the drive circuitry includes an active thin-film transistor (TFT) matrix for driving antenna elements of an array of RF radiating antenna elements in a metamaterial antenna, and using the techniques disclosed herein can reduce the number routing lines needed for supplying signal to and/or from the drive circuitry.

One technique disclosed herein to reduce the congestion will be moving some of the lines (e.g., metal routing lines) to different metal layers. In some embodiments, the different metal layers are power planes. Thus, in some embodiments, the reduction in routing lines is achieved by replacing direct current (DC) routing lines with power planes. In some embodiments, the power planes are in parallel to with iris metal layer for forming irises (slots) of the RF radiating antenna elements. An example of this metal layer is described in more detail below.

The following disclosure discusses examples of antenna embodiments followed by examples of power planes being used in place of routing lines in an antenna.

Examples of Antenna Embodiments

The techniques described herein may be used with a variety of flat panel satellite antennas. Embodiments of such flat panel antennas are disclosed herein. In some embodiments, the flat panel satellite antennas are part of a satellite terminal. The flat panel antennas include one or more arrays of antenna elements on an antenna aperture.

In some embodiments, the antenna aperture is a metasurface antenna aperture, such as, for example, the antenna apertures described below. In some embodiments, the antenna elements comprise radio-frequency (RF) radiating antenna elements. In some embodiments, the antenna elements include tunable devices to tune the antenna elements. Examples of such tunable devices include diodes and varactors such as, for example, described in U.S. Pat. No. 11,489,266, entitled “Metasurface Antennas Manufactured with Mass Transfer Technologies,” issued Nov. 1, 2022. In some other embodiments, the antenna elements comprise liquid crystal (LC)-based antenna elements, such as, for example, those disclosed in U.S. Pat. No. 9,887,456, entitled “Dynamic Polarization and Coupling Control from a Steerable Cylindrically Fed Holographic Antenna”, issued Feb. 6, 2018, or other RF radiating antenna elements. It should be appreciated that other tunable devices such as, for example, but not limited to, tunable capacitors, tunable capacitance dies, packaged dies, micro-electromechanical systems (MEMS) devices, or other tunable capacitance devices, could be placed into an antenna aperture or elsewhere in variations on the embodiments described herein.

In some embodiments, the antenna aperture having the one or more arrays of antenna elements is comprised of multiple segments that are coupled together. In some embodiments, when coupled together, the combination of the segments form groups of antenna elements (e.g., closed concentric rings of antenna elements concentric with respect to the antenna feed, etc.). For more information on antenna segments, see U.S. Pat. No. 9,887,455, entitled “Aperture Segmentation of a Cylindrical Feed Antenna”, issued Feb. 6, 2018.

illustrates an exploded view of some embodiments of a flat-panel antenna. Referring to, antennacomprises a radome, a core antenna, antenna support plate, antenna control unit (ACU), a power supply unit, terminal enclosure platform, comm (communication) module, and RF chain.

Radomeis the top portion of an enclosure that encloses core antenna. In some embodiments, radomeis weatherproof and is constructed of material transparent to radio waves to enable beams generated by core antennato extend to the exterior of radome.

In some embodiments, core antennacomprises an aperture having RF radiating antenna elements. These antenna elements act as radiators (or slot radiators). In some embodiments, the antenna elements comprise scattering metamaterial antenna elements. In some embodiments, the antenna elements comprise both Receive (Rx) and Transmit (Tx) irises, or slots, that are interleaved and distributed on the whole surface of the antenna aperture of core antenna. Such Rx and Tx irises may be in groups of two or more sets where each set is for a separately and simultaneously controlled band. Examples of such antenna elements with irises are described in U.S. Pat. No. 10,892,553, entitled “Broad Tunable Bandwidth Radial Line Slot Antenna”, issued Jan. 12, 2021.

In some embodiments, the antenna elements comprise irises (iris openings) and the aperture antenna is used to generate a main beam shaped by using excitation from a cylindrical feed wave for radiating the iris openings through tunable elements (e.g., diodes, varactors, patch, etc.). In some embodiments, the antenna elements can be excited to radiate a horizontally or vertically polarized electric field at desired scan angles.

In some embodiments, a tunable element (e.g., diode, varactor, patch etc.) is located over each iris slot. The amount of radiated power from each antenna element is controlled by applying a voltage to the tunable element using a controller in ACU. Traces in core antennato each tunable element are used to provide the voltage to the tunable element. The voltage tunes or detunes the capacitance and thus the resonance frequency of individual elements to effectuate beam forming. The voltage required is dependent on the tunable element in use. Using this property, in some embodiments, the tunable element (e.g., diode, varactor, LC, etc.) integrates an on/off switch for the transmission of energy from a feed wave to the antenna element. When switched on, an antenna element emits an electromagnetic wave like an electrically small dipole antenna. Note that the teachings herein are not limited to having unit cell that operates in a binary fashion with respect to energy transmission. For example, in some embodiments in which varactors are the tunable element, there are 32 tuning levels. As another example, in some embodiments in which LC is the tunable element, there are 16 tuning levels.

A voltage between the tunable element and the slot can be modulated to tune the antenna element (e.g., the tunable resonator/slot). Adjusting the voltage varies the capacitance of a slot (e.g., the tunable resonator/slot). Accordingly, the reactance of a slot (e.g., the tunable resonator/slot) can be varied by changing the capacitance. Resonant frequency of the slot also changes according to the equation

where f is the resonant frequency of the slot and L and C are the inductance and capacitance of the slot, respectively. The resonant frequency of the slot affects the energy coupled from a feed wave propagating through the waveguide to the antenna elements.

In particular, the generation of a focused beam by the metamaterial array of antenna elements can be explained by the phenomenon of constructive and destructive interference, which is well known in the art. Individual electromagnetic waves sum up (constructive interference) if they have the same phase when they meet in free space to create a beam, and waves cancel each other (destructive interference) if they are in opposite phase when they meet in free space. If the slots in core antennaare positioned so that each successive slot is positioned at a different distance from the excitation point of the feed wave, the scattered wave from that antenna element will have a different phase than the scattered wave of the previous slot. In some embodiments, if the slots are spaced one quarter of a wavelength apart, each slot will scatter a wave with a one fourth phase delay from the previous slot. In some embodiments, by controlling which antenna elements are turned on or off (i.e., by changing the pattern of which antenna elements are turned on and which antenna elements are turned off) or which of the multiple tuning levels is used, a different pattern of constructive and destructive interference can be produced, and the antenna can change the direction of its beam(s).

In some embodiments, core antennaincludes a coaxial feed that is used to provide a cylindrical wave feed via an input feed, such as, for example, described in U.S. Pat. No. 9,887,456, entitled “Dynamic Polarization and Coupling Control from a Steerable Cylindrically Fed Holographic Antenna”, issued Feb. 6, 2018 or in U.S. Pat. No. 11,489,266, entitled “Metasurface Antennas Manufactured with Mass Transfer Technologies,” issued Nov. 1, 2022. In some embodiments, the cylindrical wave feed feeds core antennafrom a central point with an excitation that spreads outward in a cylindrical manner from the feed point. In other words, the cylindrically fed wave is an outward travelling concentric feed wave. Even so, the shape of the cylindrical feed antenna around the cylindrical feed can be circular, square or any shape. In some other embodiments, a cylindrically fed antenna aperture creates an inward travelling feed wave. In such a case, the feed wave most naturally comes from a circular structure.

In some embodiments, the core antenna comprises multiple layers. These layers include the one or more substrate layers forming the RF radiating antenna elements. In some embodiments, these layers may also include impedance matching layers (e.g., a wide-angle impedance matching (WAIM) layer, etc.), one or more spacer layers and/or dielectric layers. Such layers are well-known in the art.

Antenna support plateis coupled to core antennato provide support for core antenna. In some embodiments, antenna support plateincludes one or more waveguides and one or more antenna feeds to provide one or more feed waves to core antennafor use by antenna elements of core antennato generate one or more beams.

ACUis coupled to antenna support plateand provides controls for antenna. In some embodiments, these controls include controls for drive electronics for antennaand a matrix drive circuitry to control a switching array interspersed throughout the array of RF radiating antenna elements. In some embodiments, the matrix drive circuitry uses unique addresses to apply voltages onto the tunable elements of the antenna elements to drive each antenna element separately from the other antenna elements. In some embodiments, the drive electronics for ACUcomprise commercial off-the shelf LCD controls used in commercial television appliances that adjust the voltage for each antenna element.

More specifically, in some embodiments, ACUsupplies an array of voltage signals to the tunable devices of the antenna elements to create a modulation, or control, pattern. The control pattern causes the elements to be tuned to different states. In some embodiments, ACUuses the control pattern to control which antenna elements are turned on or off (or which of the tuning levels is used) and at which phase and amplitude level at the frequency of operation. The elements are selectively detuned for frequency operation by voltage application. In some embodiments, multistate control is used in which various elements are turned on and off to varying levels, further approximating a sinusoidal control pattern, as opposed to a square wave (i.e., a sinusoid gray shade modulation pattern).

In some embodiments, ACUalso contains one or more processors executing the software to perform some of the control operations. ACUmay control one or more sensors (e.g., a GPS receiver, a three-axis compass, a 3-axis accelerometer, 3-axis gyro, 3-axis magnetometer, etc.) to provide location and orientation information to the processor(s). The location and orientation information may be provided to the processor(s) by other systems in the earth station and/or may not be part of the antenna system.

Antennaalso includes a comm (communication) moduleand an RF chain. Comm moduleincludes one or more modems enabling antennato communicate with various satellites and/or cellular systems, in addition to a router that selects the appropriate network route based on metrics (e.g., quality of service (QoS) metrics, e.g., signal strength, latency, etc.). RF chainconverts analog RF signals to digital form. In some embodiments, RF chaincomprises electronic components that may include amplifiers, filters, mixers, attenuators, and detectors.

Antennaalso includes power supply unitto provide power to various subsystems or parts of antenna.

Antennaalso includes terminal enclosure platformthat forms the enclosure for the bottom of antenna. In some embodiments, terminal enclosure platformcomprises multiple parts that are coupled to other parts of antenna, including radome, to enclose core antenna.

illustrates an example of a communication system that includes one or more antennas described herein. Referring to, vehicleincludes an antenna. In some embodiments, antennacomprises antennaof.

In some embodiments, vehiclemay comprise any one of several vehicles, such as, for example, but not limited to, an automobile (e.g., car, truck, bus, etc.), a maritime vehicle (e.g., boat, ship, etc.), airplanes (e.g., passenger jets, military jets, small craft planes, etc.), etc. Antennamay be used to communicate while vehicleis either on-the-pause, or moving. Antennamay be used to communicate to fixed locations as well, e.g., remote industrial sites (mining, oil, and gas) and/or remote renewable energy sites (solar farms, windfarms, etc.).

In some embodiments, antennais able to communicate with one or more communication infrastructures (e.g., satellite, cellular, networks (e.g., the Internet), etc.). For example, in some embodiments, antennais able to communicate with satellites(e.g., a GEO satellite) and(e.g., a LEO satellite), cellular network(e.g., an LTE, etc.), as well as network infrastructures (e.g., edge routers, Internet, etc.). For example, in some embodiments, antennacomprises one or more satellite modems (e.g., a GEO modem, a LEO modem, etc.) to enable communication with various satellites such as satellite(e.g., a GEO satellite) and satellite(e.g., a LEO satellite) and one or more cellular modems to communicate with cellular network. For another example of an antenna communicating with one or more communication infrastructures, see U.S. patent Ser. No. 16/750,439, entitled “Multiple Aspects of Communication in a Diverse Communication Network”, and filed Jan. 23, 2020.

In some embodiments, to facilitate communication with various satellites, antennaperforms dynamic beam steering. In such a case, antennais able to dynamically change the direction of a beam that it generates to facilitate communication with different satellites. In some embodiments, antennaincludes multi-beam beam steering that allows antennato generate two or more beams at the same time, thereby enabling antennato communication with more than one satellite at the same time. Such functionality is often used when switching between satellites (e.g., performing a handover). For example, in some embodiments, antennagenerates and uses a first beam for communicating with satelliteand generates a second beam simultaneously to establish communication with satellite. After establishing communication with satellite, antennastops generating the first beam to end communication with satellitewhile switching over to communicate with satelliteusing the second beam. For more information on multi-beam communication, see U.S. Pat. No. 11,063,661, entitled “Beam Splitting Hand Off Systems Architecture”, issued Jul. 13, 2021.

In some embodiments, antennauses path diversity to enable a communication session that is occurring with one communication path (e.g., satellite, cellular, etc.) to continue during and after a handover with another communication path (e.g., a different satellite, a different cellular system, etc.). For example, if antennais in communication with satelliteand switches to satelliteby dynamically changing its beam direction, its session with satelliteis combined with the session occurring with satellite.

Thus, the antennas described herein may be part of a satellite terminal that enables ubiquitous communications and multiple different communication connections.

In some embodiments, antennacomprises a metasurface RF antenna having multiple RF radiating antenna elements that are tuned to desired frequencies using RF antenna element drive circuitry. The drive circuitry can include a drive transistor (e.g., a thin film transistor (TFT) (e.g., CMOS, NMOS, etc.), low or high temperature polysilicon transistor, memristor, etc.), a Microelectromechanical systems (MEMS) circuit, or other circuit for driving a voltage to an RF radiating antenna element. In some embodiments, the drive circuitry comprises an active-matrix drive. In some embodiments, the frequency of each antenna element is controlled by an applied voltage. In some embodiments, this applied voltage is also stored in each antenna element (pixel circuit) until the next voltage writing cycle.

Power Planes for an RF Metamaterial Antenna

Embodiments described herein include antennas that use power planes to provide one or more voltages to RF element driving circuits or other circuits of an antenna layout. In some embodiments, the voltage supplied by each power plane is a constant, direct conversion (DC) voltage. The constant voltage can be used to keep one or more nodes in each of the RF element driving circuits or other circuits at a constant voltage.

In some embodiments, the power planes replace the number of routing lines that would have been used to route voltages to the RF element driving circuits and/or RF metamaterial antenna elements. This usage of power planes instead of routing lines is important for designs with high RF antenna element density and limited layout space. In some embodiments, the antenna includes the metal power planes in parallel geometrically with an iris metal layer forming a part of the RF antenna elements, separated with a passivation layer, to supply DC voltages to RF element driving circuits and/or RF metamaterial antenna elements.

If a DC voltage provided by the RF element driving circuit and required for the antenna element (to drive the antenna element) is being applied using a power plane metal layer, then no patterning similar to routing lines carrying array addressing signals is needed. This provides additional routing flexibility for the order in which RF elements are connected to the power plane metal layer (though the RF element driving circuit) as it is not carrying an array addressing signal so it does not need to follow a particular route or path.

illustrates some embodiments of a portion of an antenna aperture having power planes to supply voltages to RF antenna element driving circuits of an RF metamaterial antenna. In some embodiments, the antenna is a metasurface antenna as described above. Referring to, the antenna aperture includes RF antenna elements, keepout areasfor each of the RF antenna elements, routing linesand RF antenna element driving circuits. In some embodiments, each of the RF antenna elementsis electrically coupled to receive a drive voltage and/or other signals from at least one of the RF element driving circuits. In some embodiments, RF antenna elementscomprise RF radiating metamaterial antenna elements. In some embodiments, routing linescomprise control signal, timing signal, and/or data signal routing to and/or between RF antenna element driving circuits. Note that there can be other routing lines to route signals to other circuit elements in the antenna.

As shown in, the antenna aperture includes multiple power plane segments. The areas for power plane segmentsare defined by the dashed lines. In some embodiments, power plane segmentsare all part of the same power plane (e.g., one piece of metal). In some other embodiments, power plane segmentsare coupled to and electrically connected to each other to form a single power plane. In some embodiments, the power planes comprise an interconnected mesh of metal lines. Such an implementation reduces the potential for shorting and reduces the metal area.

In some embodiments, power plane segmentstransfer a common, constant voltage to all of RF antenna driving circuits electrically connected to one of power plane segments. In some embodiments, the RF antenna element driving circuitssupply drive, or tuning, voltages to the RF radiating antenna elements, and each of power plane segmentsis coupled to supply a common voltage to multiple RF antenna driving circuits. In some embodiments, power plane segmentsare used only for signals transferring a direct current (DC), common voltage at the same time in place of separate routing lines like routing lines. This reduces the number of routing lines running between antenna elements in the aperture.

In some embodiments, one of power plane segmentsis electrically connected to an RF antenna element driving circuitusing a via structure to at least a portion of RF element driving circuit. In some embodiments, the via structure could be a single via or a structure of multiple vias to form a contact between top and bottom metal layers using intermediate metal layers to bridge between them. In some embodiments, each of RF antenna driving circuitshas a footprint and the via structure extends below the footprint and extends from that point over to one of one of the power plane segments. In some other embodiments, one of power plane segmentsis electrically connected to an RF antenna element driving circuitusing a via structure that is located proximate to, or near, RF antenna element driving circuit. In some embodiments, each of RF antenna element driving circuitshas a footprint and the via structure extends below its footprint. In this case, the via structure can electrically connect one of power plane segmentsto an additional metal layer at a node, which is routed into RF antenna element driving circuitfrom that point. This additional metal layer can be a routing metal layer (e.g., routing layerof) or the additional metal layer can be a metal plate (e.g., a capacitor plate, etc.) and can be dependent upon the layout of the RF antenna element driving circuit (e.g., the TFT box layout in a matrix drive, etc.).

In some other embodiments, the node is within RF antenna element driving circuitand a part of power planeextends into the area of RF antenna element driving circuitto electrically connect one of power plane segmentsdirectly into RF antenna element driving circuitwithout the use of routing metal from outside RF antenna element driving circuit. This could allow the via structure to be placed in an advantageous place in the RF element driving circuit, such as on a node of the circuit, without creating an extra wire.

In some embodiments, the power plane is electrically connected to the RF antenna element (pixel circuit) using a metal extension (e.g., like a finger) on the same metal layer near the driving circuitry of the RF element driving circuit that provides a drive voltage to the RF antenna element. In some embodiments, this is accomplished by modifying the keepout layer in each RF element drive circuits to bring an extension of the power plane into the RF element driving circuit box. For example, the keepout area incan be modified so that the power plane is not completely excluded from the RF element driving circuit.

illustrates an example of a via structure electrically connecting an RF antenna element driving circuit (or RF antenna element) to a power plane. Referring to, power planeis connected electrically to nodethat is coupled to a RF antenna element driving circuit. In some embodiments, power planecomprises a metal layer. In some embodiments, there are one or more layersA between power planeand nodethrough which via structureextends. Via structurecan include metal and/or dielectric layers. In some embodiments, the metal layer of power planeis on top of (e.g., deposited on) one or more other layersB (e.g., semiconductor fabrication processing layers). Also, in some embodiments, if there are multiple power plane metal layers, then the via structure can have multiple vias. This is particularly true in the case that the stack up of has multiple layers of metals and dielectrics, or the dielectrics become thicker (e.g., to prevent shorts, to prevent cross talk), one might need to stack or step vias to manage the structure area and/or obey design rules. Nodeis coupled to an RF element driving circuit via metal layer. Metal layercan comprise one of the metal layers used for routing.

also shows the coupling arrangement in which a node is not within the RF antenna element driving circuit and is coupled to the RF antenna element driving circuit via a metal layer (e.g., routing lines, capacitive plate, etc.). Referring to, a nodeof an RF element driving circuitis coupled to a via structureusing a metal layer. Also shown in, routing linesare coupled to RF element driving circuitto transfer control signal, timing signal, and/or data signal routing to and/or from RF antenna element driving circuit. A keepout areais around RF element driving circuitand defines an edge of the power plane. Routing linesroute signals (e.g., voltage signals) to an RF antenna element. Power plane keepout areaextends around routing lines.